Benzodiazepine compounds have conventionally been known as anxiolytic drugs. Recently, Buspirone [N-(4-(4-(2-pyrimidinyl)-1-piperazinyl)butyl)-1,1-cyclopentanediacetamide hydrochloride] and other compounds have become recognized as new anxiolytic drugs with action mechanisms different from those of the benzodiazepines, but the advent of newer anxiolytic drugs is being desired.
Taking notice of the piperazine derivatives, the present inventors earnestly investigated to develop compounds which may be used as anxiolytic drugs. A variety of piperazine derivatives have been recognized to have a satisfactory antihypertensive effect (for example, Japanese Patent Application Laying-Open (KOKAI) No. 57-80379, No. 57-114588, No. 58-24563 and No. 58-154573, but were not known to have anxiolytic activities.
Now, the present inventors have discovered that certain piperazine derivatives and their acid addition salts have satisfactory anxiolytic effects, and thus the present invention has been completed.